Time filter

Source Type

Chino Hills, CA, United States

Hao T.,15905 Tanberry Dr.
Soft Matter | Year: 2015

The tap density of granular powders was found to be better fitted with the stretched exponential law. In our previous work, the stretched exponential tap density equations were derived with the rate process theory and free volume concept, under the assumption that the particle packing rate during the tapping process obeys the stretched Arrhenius equation, which, however, has an empirical origin. In this article, the above assumption is eliminated and attempts are made to obtain the stretched exponential tap density equations from very fundamental bases. In a vertical tapping process, the probability of particles attaining certain energy states is assumed to obey the Boltzmann distribution and particles traveling from one site to another are assumed to follow a very common memoryless random exponential law. The stretched exponential tap density equations are thus derived and all parameters acquire clear physical meanings. The most important parameter, the stretched exponential, is demonstrated to correlate with the interparticle forces: A small value may indicate a strong adhesive or cohesive interaction. Therefore, the stretched exponential could be a better indicator for powder flowability correlated with particle interactions as well. © The Royal Society of Chemistry 2015.

The underlying relationships among viscosity equations of glass liquids and colloidal suspensions are explored with the aid of free volume concept. Viscosity equations of glass liquids available in literature are focused and found to have a same physical basis but different mathematical expressions for the free volume. The glass transitions induced by temperatures in glass liquids and the percolation transition induced by particle volume fractions in colloidal suspensions essentially are a second order phase transition: both those two transitions could induce the free volume changes, which in turn determines how the viscosities are going to change with temperatures and/or particle volume fractions. Unified correlations of the free volume to both temperatures and particle volume fractions are thus proposed. The resulted viscosity equations are reducible to many popular viscosity equations currently widely used in literature; those equations should be able to cover many different types of materials over a wide temperature range. For demonstration purpose, one of the simplified versions of those newly developed equations is compared with popular viscosity equations and the experimental data: it can well fit the experimental data over a wide temperature range. The current work reveals common physical grounds among various viscosity equations, deepening our understanding on viscosity and unifying the free volume theory across many different systems. © the Owner Societies 2015.

Inspired by the Marcus theory of electron transfer, electrical conductivity equations without reference to any specific materials are derived on the basis of Eyring's rate process theory and the free volume concept. The basic assumptions are that electrons are assumed to have a spherical physical shape with an imaginary effective radius inferred from the latest experimental evidence; electrons traveling from one equilibrium position to another obey Eyring's rate process theory; and the traveling distance is governed by the free volume available for electrons to transport. The derived equations fit very well with experimental data, and seem to trend consistently with the currently observed experimental phenomena, too. The obtained equations predict that superconductivity happens only when electrons form certain structures of a small coordinate number like electron pairs, with the coordinate number equal to 1 at low temperatures, which is in line with the popular Cooper pairs concept in the BCS theory for superconductivity. The current work may provide new insights into the rich conductive behaviors at low temperatures. © The Royal Society of Chemistry 2015.

The common charging agents and charging mechanisms in non-aqueous multiphase systems available in the literature are analyzed, and the conductivity equations derived on the basis of the charging mechanisms with the Eyring's rate process theory are compared with experimental observations. The popular charging mechanisms in non-aqueous systems, such as the ion preferential absorption, ion pair dissociation, and micelle disproportionation/fluctuation models, are found to be incapable of explaining all experimental evidences. Particularly, the ion pair dissociation and micelle disproportionation/fluctuation models apparently suffer a major drawback: how charges are separated and most importantly how charging entities are stabilized in non-aqueous systems, are not adequately addressed; in low dielectric constant non-aqueous media separated ions tend to bind together rather than stay separately. A new charging mechanism incorporating an electric field internally available or externally applied into the charging process is proposed to explain charge separations and stabilizations. The conductivity equations derived on the basis of this new mechanism predict that conductivity should linearly increase with both the electric field and the concentrations of inverse micelles in very low concentration regions, which is consistent with experimental evidences. © 2016 the Owner Societies.

Discover hidden collaborations